//
// Created by 李梦凡 on 2019/10/20.
//

#include "resource_manager.h"

#include <iostream>
#include <sstream>
#include <fstream>

#define STB_IMAGE_IMPLEMENTATION

#include <stb_image.h>

// Instantiate static variables
std::map<std::string, Texture2D>    ResourceManager::Textures;
std::map<std::string, Shader>       ResourceManager::Shaders;


Shader ResourceManager::LoadShader(const GLchar *vShaderFile, const GLchar *fShaderFile, const GLchar *gShaderFile,
                                   std::string name) {
    Shaders[name] = loadShaderFromFile(vShaderFile, fShaderFile, gShaderFile);
    return Shaders[name];
}

Shader ResourceManager::GetShader(std::string name) {
    return Shaders[name];
}

Texture2D ResourceManager::LoadTexture(const GLchar *file, GLboolean alpha, std::string name) {
    Textures[name] = loadTextureFromFile(file, alpha);
    return Textures[name];
}

Texture2D ResourceManager::GetTexture(std::string name) {
    return Textures[name];
}

void ResourceManager::Clear() {
    // (Properly) delete all shaders
    for (const auto &iter : Shaders) {
        glDeleteProgram(iter.second.ID);
    }
    Shaders.clear();
    // (Properly) delete all textures
    for (const auto &iter : Textures) {
        glDeleteTextures(1, &iter.second.ID);
    }
    Textures.clear();
}

Shader
ResourceManager::loadShaderFromFile(const GLchar *vShaderFile, const GLchar *fShaderFile, const GLchar *gShaderFile) {
    // 1. Retrieve the vertex/fragment source code from filePath
    std::string vertexCode;
    std::string fragmentCode;
    std::string geometryCode;
    try {
        // Open files
        std::ifstream vertexShaderFile(vShaderFile);
        std::ifstream fragmentShaderFile(fShaderFile);
        std::stringstream vShaderStream, fShaderStream;
        // Read file's buffer contents into streams
        vShaderStream << vertexShaderFile.rdbuf();
        fShaderStream << fragmentShaderFile.rdbuf();
        // close file handlers
        vertexShaderFile.close();
        fragmentShaderFile.close();
        // Convert stream into string
        vertexCode = vShaderStream.str();
        fragmentCode = fShaderStream.str();
        // If geometry shader path is present, also load a geometry shader
        if (gShaderFile != nullptr) {
            std::ifstream geometryShaderFile(gShaderFile);
            std::stringstream gShaderStream;
            gShaderStream << geometryShaderFile.rdbuf();
            geometryShaderFile.close();
            geometryCode = gShaderStream.str();
        }
    }
    catch (std::exception e) {
        std::cout << "ERROR::SHADER: Failed to read shader files" << std::endl;
    }
    const GLchar *vShaderCode = vertexCode.c_str();
    const GLchar *fShaderCode = fragmentCode.c_str();
    const GLchar *gShaderCode = geometryCode.c_str();
    // 2. Now create shader object from source code
    Shader shader;
    shader.Compile(vShaderCode, fShaderCode, gShaderFile != nullptr ? gShaderCode : nullptr);
    return shader;
}

Texture2D ResourceManager::loadTextureFromFile(const GLchar *file, GLboolean alpha) {
    // Create Texture object
    Texture2D texture;
    if (alpha) {
        texture.Internal_Format = GL_RGBA;
        texture.Image_Format = GL_RGBA;
        texture.Wrap_S = GL_CLAMP_TO_EDGE;
        texture.Wrap_T = GL_CLAMP_TO_EDGE;
    }
    // Load image
    int width, height, nrComponents;
    unsigned char *image = stbi_load(file, &width, &height, &nrComponents, 0);

    // Now generate texture
    texture.Generate(width, height, image);
    // And finally free image data
    stbi_image_free(image);
    return texture;
}
